The present invention relates to secondary containment of underground piping and, more particularly, to secondary containment of the flexible hose connections between the underground fiberglass supply pipes and the emergency shut-off valves associated with aboveground pumps for dispensing hydrocarbon fuels.
As part of the effort to protect the environment gasoline service stations have had to install emergency shut-off valves below each gasoline pump in the island supporting the pump. The required shut-off valve is tripped either by heat from fire melting a fusible link or by having its outlet neck sheared off if a pump is knocked over or dislodged from the island. In order for the shearing protection to be effective, the valve body must be anchored rigidly to a structural member, for example, a steel angle iron or the like, within the island. The valve has to be mounted in a vertical position with its inlet directed downwardly.
Because of the corrosion problems underground, the piping from the underground storage tank is constructed at present of reinforced fiberglass which is brought up to the vicinity of the emergency shut-off valve. Heretofore, to accommodate the requisite bend from the fiberglass pipe to the valve, the two have been joined by a length of flexible hose and appropriate adapter fittings to accommodate differences in pipe diameters, materials, and valve inlet port openings. For increased protection against ground contamination, the fiberglass supply pipe is frequently surrounded by a secondary containment pipe, also of fiberglass, disposed concentrically about the primary supply pipe. To provide secondary containment of the flexible hose section, a flexible sleeve has been used by at least one manufacturer secured to the fiberglass supply pipe at one end and to the valve housing at the other end by respective metal clamps. Unfortunately, these metal clamps have proven to be a weak link in the system due to corrosion. Moreover, the known containment sleeve has not included provision for connection to a fiberglass containment pipe as distinguished from the smaller diameter primary supply pipe, and has the capability of withstanding a maximum test pressure of less than 10 p.s.i.
As a result of studying the various plumbing installations used by the numerous petroleum companies throughout the United States, it has been discovered that numerous installations surround a 2" nominal diameter supply pipe with a 3" nominal diameter containment pipe while others use the supply pipe alone. Some use an emergency shut-off valve with an externally threaded inlet stub while others do not. Some use an emergency valve with an internally threaded inlet port of 11/2" n.p.t. while others use a valve with a 2" n.p.t. inlet port. And in a few instances an enclosure is disposed about the valve with a short stack surrounding the valve inlet stub, it being contemplated that a containment sleeve be coupled to the stack.